Campaigners Tour England Before Brexit Vote

— London -- Campaigners in England are making one last push with voters before tomorrow's groundbreaking referendum on whether the country should stay in the European Union.

British Prime Minister David Cameron said today that there is no coming back if Britain leaves the E.U. and that a Brexit will hurt the British economy and adversely impact opportunities for future generations.

"You can't jump out the aeroplane and then clamber back through the cockpit hatch," he told the BBC.

Cameron's campaign schedule today included a visit to a farm, meetings with business owners and chats with school children.

Leading Brexit campaigner, Boris Johnson, a former mayor of London, visited a fish market where he urged voters to “believe in” their country.

“This is a crucial time, lots of people will be making up their minds, and I hope very much they will believe in our country, believe in what we can do,” he said.

Social media users criticized the "Leave" campaign after a plane carrying a banner with the slogan “Vote Leave, Take Back Control” was seen flying over Trafalgar Square as the husband of the late British politician Jo Cox gave a speech celebrating her on what would have been her 42nd birthday.

Another plane carrying a banner with the word “Remain” has been flying over some of London's landmarks such as the London Eye and the House of Parliament.

More than 46 million people have a chance to vote tomorrow, the largest electorate ever for a U.K. poll, according to Jenny Watson, chair of the Electoral Commission, who will announce the result of the vote. She is expected to announce the vote Friday morning in Manchester.

The polls suggest that it will be a very close race that can go either way, although the “Remain” camp has seen a boost in support in recent days.

More than 1,280 business leaders have signed an open letter backing the U.K.’s membership of the E.U., while entrepreneur Sir James Dyson and local businesses, including one of the U.K.'s oldest firms, Tate & Lyle Sugars, have made the case for leaving the E.U.

British celebrities including David Beckham, Simon Cowell and U2 have declared their support for the "Remain" campaign.